<!DOCTYPE html>
<html lang="zh">
    <head>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <meta http-equiv="X-UA-Compatible" content="ie=edge">
        <title>欢迎来到德莱联盟</title>
    </head>
    <body>
    </body>
    <script>
        function visibilityChange(){
            if(document.hidden){
                document.title = "哎！别走啊"
            } else {
                document.title = "我就知道你会回来的~~"
            }
        }

        document.addEventListener("visibilitychange", visibilityChange)
    </script>
</html>